Getting started on writing a driver for the rpi4

Getting started on writing a driver for the rpi4

[Jacko Dirks]

Hello all,

I want to get started on writing a driver for the I2C slave for the
Raspberry Pi 4. Now, I have a feeling that I cannot just write the thing
and then dump it on everyone involved, not in the last place because I
have never submitted a kernel patch before. So, should I email a mailing
list warning everyone of what I want to do? Is there anything else I
should know about?

To clarify, this is not about the creation of the driver itself, more of
a meta question of how to announce that I want to do this.

Thanks in advance,

Jacko Dirks

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Re: Getting started on writing a driver for the rpi4

[Valdis Klētnieks]

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On Sun, 03 May 2020 22:19:35 +0200, Jacko Dirks said:
> have never submitted a kernel patch before. So, should I email a mailing
> list warning everyone of what I want to do? Is there anything else I
> should know about?

Yes, you should do a bit of Googling and/or check the current source tree
to make sure you aren't re-inventing the wheel.. There may already be
working or near-working code,  A quick Google check foud:

Somebody else was looking at the problem back in February.
https://www.raspberrypi.org/forums/viewtopic.php?t=265832

http://abyz.me.uk/rpi/pigpio/python.html apparently includes some slave
functionality from userspace that may be useful as a guide:

I2C/SPI SLAVE
bsc_xfer	I2C/SPI as slave transfer
bsc_i2c	I2C as slave transfer

> To clarify, this is not about the creation of the driver itself, more of
> a meta question of how to announce that I want to do this.

Pretty much nobody cares that you *want* to do it. GitHub and SourceForge
are full of abandonware where somebody *wanted* to do something and never
finished it.

Once you have a driver that loads and semi/mostly works, *then* you announce it, usually
in the form of a patch stream generated using 'git format-patch' and 'git send-email'.

But Greg KH can't even add it to drivers/staging until you have at least a good first pass
at workig code...

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